I even find it cool that Apple sometimes doesn't comment on certain product news that we might naturally discover, such as "details that she only cares about." But there are some that are inexplicable.
The German Website Mac & i unintentionally discovered (Google Translate) that OS X El Capitan enabled on Retina display iMacs (both 27-inch 5K and 21.5-inch 4K) support for 10 bit color in pictures.
The novelty should further enhance the image quality of these machines, especially in gradient graphics; it is now 1,024 gradations per color channel (ie 30 bits in total summing R, G and B). But, of course, the differences are not readily apparent to the average user, which may justify Apple not commenting on it.
Interestingly, Windows has already supported 10 bits since version 7. This is great especially for those who work with photo and video.
(via Cult of Mac)